The typical course of the planning phase for a refractive treatment includes, i.a., the upload of input data corresponding to a desired refractive correction, specification of the desired correction, creation of the treatment pattern, and upload of the data onto a therapeutic platform, i.e. a laser treatment system. The desired refractive correction may be based on diagnostic data obtained by at least one of a subjective refractive error and a measured objective refractive error. The measured refractive error may be obtained by at least one of a wavefront sensor, topographical measurement device or a pachymetry measurement device. Low order aberrations may be determined by a subjective refractive error, e.g. considering the verbal feedback of a patient.
The generated corneal shape change profile, e.g. a simulated ablation pattern of an excimer laser or a volumetric femtosecond removal profile, may be disclosed in a graphical user interface GUI or an other implementation. The volumetric profile describes the amount of microns of corneal tissue which is planned to be removed in a certain 3 dimensional location on or in the cornea. Tissue on the cornea, i.e., on the surface of the cornea may be removed, e.g., by an excimer laser and tissue in the cornea, i.e., an intrastromal effect may be caused by a femtosecond laser.
In the determination of a refractive treatment checks may be applied, e.g., whether the corneal thickness after a treatment is still sufficient such that the treatment is applicable. In presently available systems the person controlling a treatment apparatus, usually a physician, finally decides whether a treatment is conducted, i.a., based on a GUI or an other implementation as outlined above.
One of the continuously developing usability and regulatory requirements is to ensure a certain level of usability comfort and applicable safety to the user, i.e., to make refractive treatments safe and more reliable and demonstrate this in an easy but quantitative way to the user. The sole observation of simulated ablation patterns may not be sufficient any more for future applications.
There is a need to provide an independent check that the created ablation pattern is actually related to the desired refractive correction.
Document WO-A-98/40041, from Chiron Technolas GmbH Ophthalmologische Systeme, relates to a simulation of a laser treatment on the eye by pretreating a contact lens. The treated contact lens is placed on the patient's eye and the patient's resulting visual acuity is measured. If within acceptable limits, the treatment is then performed on the patient's eye. Otherwise, the treatment pattern is adjusted.
An aspect of the invention is to provide a method and an apparatus for determining whether the volumetric ablation relating to a certain treatment pattern is within predefined tolerances, i.e., to provide an independent check of the applicability of the created volumetric profile.